program for simple calculator in c++

#include<iostream.h>
#include<conio.h>
#include<math.h>
#include<process.h>
int main()
 {
 clrscr();
 char ch,ch1;
 float a,b,add,sub,multi,div;
 cout<<"\nsimple calculator:";
 cout<<"\n1.Addition";
 cout<<"\n2.Subtraction";
 cout<<"\n3.Multiplication";
 cout<<"\n4.Division";
 cout<<"\n5.Exit"<<"\n";
 cout<<"Enter your choice:";
 do
 {
 cin>>ch;
 if(ch=='1'|| ch=='2'|| ch=='3'|| ch=='4')
 {
 cout<<"Enter the value of a:";
 cin>>a;
 cout<<"Enter the value of b:";
 cin>>b;
 }
 switch(ch)
 {
 case'1':add=a+b;
       cout<<"Addition="<<add;
       break;
 case'2':sub=a-b;
       cout<<"Subtraction="<<sub;
       break;
 case'3':multi=a*b;
       cout<<"Multiplication="<<multi;
       break;
 case'4':if(b==0)
  cout<<"Divide by Zero error!!!";
  else
  div=b/a;
       cout<<"Division="<<div;
       break;
 case'5':cout<<"breaking:";
 exit(0);
 default:cout<<"Wrong choice!!!";
cout<<"Enter a valid one";
break;
 }

cout<<"\nWant to enter more (y/n)?";
cin>>ch1;
if(ch1=='y'|| ch1=='y')
cout<<"again enter your choice (1-5):";
}
while(ch1=='y'|| ch1=='y');
getch();
return(0);
}